In some wireless networking schemes, data is communicated using packets that are transmitted in a random access fashion through a wireless channel. The receiver in such an arrangement does not know when a packet will be received and must therefore monitor the wireless channel and attempt to detect a packet when it arrives. Packet detection may be performed by correlating an input signal of the receiver with another signal to generate a correlation coefficient. The input signal may be cross-correlated with a pattern known to be within a header of each packet or auto-correlated with itself to generate the correlation coefficient. Once the correlation coefficient has been generated, it may be compared to a fixed threshold value to determine whether a packet has arrived. It is assumed that a packet has arrived if the correlation coefficient is greater than the fixed threshold value.
In the past, it was often assumed that the only form of noise present at the input of a radio frequency (RF) receiver in a wireless device was white Gaussian noise. White Gaussian noise is a random, uncorrelated form of noise that has little to no effect on the correlation coefficient that is generated by the receiver during packet detection operations. Investigation has shown, however, that other forms of noise may also be present at the input of a receiver within a wireless device that tends to increase correlation coefficients. One such noise type will be referred to herein as platform noise. Platform noise is noise that is generated within the platform itself. The source of such noise is typically the various clocks (e.g., an LCD pixel clock, a PCI express phase locked loop (PLL) clock, etc.) and other signal generating components within the platform. Unlike white Gaussian noise, it has been observed that the temporal correlation of platform noise is typically high. Therefore, the platform noise may not have a negligible effect on the correlation calculation performed during packet detection operations.
If platform noise alone results in a correlation coefficient that is higher than the fixed threshold value used by a receiver, then the receiver will improperly indicate that a packet has been detected. This situation is known as a false alarm. When a false alarm occurs, further receiver processing may be performed before it is realized that the detection was a false alarm. After this is realized, the receiver state may be reset to acquisition mode. If an actual packet is received before the receiver state is reset, the packet may not be detected by the receiver. The missed packet will then have to be retransmitted, resulting in a reduction in throughput in the network. It is desirable that receiver techniques be developed that are capable of increasing a packet detection rate in a wireless network receiver.